GM-CSF stands for granulocyte monocyte colony stimulating factor. GM-CSF is a naturally occurring substance that is made by the body in response to infection or inflammation. It acts on the bone marrow to increase the number of two types of white blood cells that fight infection, granulocytes (neutrophils) and monocytes, and makes them more effective. GM-CSF has no effect on the marrow cells which make red blood cells and platelets, so it does not help correct anaemia or restore low platelet counts.

The technology of genetic engineering has allowed the manufacture of G-CSF (known as recombinant human or rh, GM-CSF) for the treatment of people with low white blood cell counts. This includes some people who have had chemotherapy for cancer where it can speed up the recovery of the white cell count after treatment. This can help reduce the risk of infections and prevent delays in treatment, or even allow for higher doses of treatment to be given.

rhGM-CSF can be given either by injections under the skin or infusions (drips) into a vein.

Side effects of rhGM-CSF include include bone pain, allergic reactions, lethargy, malaise, anorexia, skin rashes, flushing, fever and chills. At high doses, weight gain is often seen along with breathing difficulties, blood clots and collections of fluid around the heart or lungs.

rhGM-CSF is also known as molgramostim or Leucomax.

Not everyone who has chemotherapy will need rhGM-CSF but if you are worried about your blood counts have a word with your doctors to check whether they think it might help you.